1. Field of the Invention
The present invention relates to an image forming apparatus such as a printer, a copying machine or a facsimile.
2. Background Art
For example, when an electro-photographic image forming apparatus is operated, noise associated with the operation of the apparatus is generated. Noise of an image forming apparatus includes, for example, a sound caused by sliding friction which is generated when a recording medium to which an image is to be transferred are conveyed.
As for the image forming apparatus, it is known that a fibrous sound absorbing material, such as polyester fiber, having sound-absorbing function in the audible region is stuck on an inner surface of an external cabinet surrounding the apparatus, so prevents noise from leaking out of the image forming apparatus, as disclosed in JP-A-2002-365985.
The inventors of the present invention have found out that the above-mentioned conventional image forming apparatus has a problem in that the image quality of an image to be transferred to a recording medium is deteriorated by the fact that fine fibers such as the sound absorbing material float in the image forming apparatus.
For example, if a fibrous sound absorbing material provided in the image forming apparatus contains carbon, fibers containing fine carbon float inside the image forming apparatus. In the image forming apparatus, if the carbon-containing fibrous materials float in the vicinity of an intermediate transfer belt 1 charged with a predetermined electric potential, as shown in FIG. 9, the carbon-containing fibrous materials are liable to stick to the intermediate transfer belt 1 in a upright state which protrude from the intermediate transfer belt 1. In this way, the inventors have found out that the carbon-containing fibrous materials sticking to the intermediate transfer belt 1 is stuck into a photoreceptor 5 in the vicinity of a primary transfer roller 4 and breaks through a photoconductive layer of the surface of the photoreceptor 5 when the intermediate transfer belt 1 rotates along belt-tensioning rollers 2 and 3.
A portion of the photoconductive layer of the photoreceptor 5 through which the carbon-containing fibrous materials breaks becomes an unrecoverable damage of the photoconductive layer, which may cause a defect in the image quality. Further, even in case the sound absorbing member is covered with a sound absorbing member cover made of air-permeable cloth in order to prevent fibers from being isolated from the sound absorbing member, if the fibers of the sound absorbing member cover are dyed black with pigment which contain carbon, noise can be prevented from leaking out of the image forming apparatus while the light-shielding effect inside the image forming apparatus can be maintained. However, since the carbon-containing fibrous materials are isolated from the sound absorbing cover, the same problem occurs.
Moreover, the carbon-containing fibrous materials which float in the image forming apparatus may cause the deterioration of image quality even when they simply stick to the photoreceptor 5 and the intermediate transfer belt 1. For example, if carbon-containing fibrous materials stick to the photoreceptor 5 or the intermediate transfer belt 1 from the time when the photoreceptor or the intermediate transfer belt is cleaned to the time when the transfer of an image therefrom is performed, a defect occurs in the image quality.